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POR-2C12(EX) (WT-2012)(EX)

EXTRACTED VERSION

OPERATION DOMINIC, FISH BOWL SERIES Project Officers Report—Project 2.1

External Neutron Flux Measurements

John W. Kinch, Project Officer US Army Nuclear Research Laboratory Edgewood Arsenal, MD

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30 December 1963

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OPERATION DOMINIC, FISH BOWL SERIES, Project Officers Report—Project 2.1 External Neutron Flux Measurements, Extracted Version

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18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number)

DOMINIC, Proj. 2.1 Star Fish Prime High Altitude Fish 3owl King Fish Nuclear Explosions Blue Gill Triple Prime Neutron Flux

19 ABSTRACT (Continue on reverse if necessary and identify by block number)

The objective of this project was to measure the neutron flux as a function of distance from high-altitude nuclear detonations. The threshold detector system was used to measure the flux. Gold, U23,5, Pu239, Np237, U238, sulfur, magnesium, aluminum, and zirconium foils were employed as detecting materials, instrument pods carried aloft by the launch vehicles were used to position the detectors near the detonation. Four sets of instruments were placed in each of three pods for Shots Blue Gill Triple Prime, King Fish and Starfish Prime.

The project was considered a success because it obtained data in all events. Ni/

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FOREWORD

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ABSTRACT

The objective of this project was to measure the neutron

llux as a function of distance from high-altitude nuclear

detonations.

The threshold detector system was used to measure the

flux. Gold, U335, Pu339, Np337, U838, sulfur, magnesium,

aluminum, and zirconium foils were employed as detecting

materials. Instrument pods carried aloft by the launch ve-

hicle were used to position the detectors near the detonation.

Four sets of instruments were placed in each of three pods

for Shots Blue Gill Triple Prime, King Fish, and Starfish

Prime.

Measurements of the neutron flux were made at three

distances from Shot Blue Gill Triple Prim;. Neutrons with

energies greater than!

Only the neutron detectors from the 2.5-km pc

covered after King Fish. These detectors showed

Measurements mde during Shot Star Fish Prime showed that

neutrons with energies greater than

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The measured total flux'

The project obtained data in all events in which it

participated and can he considered a success.

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CONTENTS

ABSTRACT 5

CHAPTER 1 INTRODUCTION 9 1.1 Objective 9 1.2 Background 9 1.3 Theory 10

CHAPTER 2 PROCEDURE 12 2.1 Operations 12 2.2 Instrumentation 14 2.3 Calibration 15 2.U Counting Equipment 16

CHAPTER 3 RESULTS 26 3.1 Neutron Flux 26 3.2 Neutron Dose 27

CHAPTER k DISCUSSION 34 k.l Neutron Flux and Dose 34 k.2 Data Reliability 35 U.3 Comparison with Predictions 36

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 41 5.1 Conclusions 41 5.2 Recommendations 41

REFERENCES 42

TABLES 2.1 Pertinent Parameters for Shots Blue Gill

Triple Prime, King Fish, and Star Fish Prime 18

2.2 Pod Information for Shots Blue Gill Triple Prime, King Fish, and Star Fish Prime ... 18

2.3 Pod Orientation Angles for Shot Star Fish Prims 19

2,k Detecting Materials, Reactions, Threshold Energies, and Effective Cross-Sections ... 19

2.5 Calibration Numbers 20

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3.1 Neutron Threshold Detector Results for Shot Blue Gill Triple Prime 28

3-2 Neutron Threshold Detector Results for Shot King Fish 29

3.3 Neutron Threshold Detector Results for Shot Star Fish Prime 30

3.1+ Gold Foil Information for Blue Gill Triple Prime 31

3-5 Gold Foil Information for King Fish 31 3.6 Gold Foil Information for Star Fish Prime ... 31 3-7 Neutron Dose Calculations for Shots Blue Gill

Triple Prime, Star Fish Prime, and King Fish . . 31 h.l Comparison of Predicted and Measured Flux

Values 38 h.2 Flux Ratios for Shot Blue Gill Triple Prime,

King Fish, and Star Fish Pria» 38

FIGURES 2.1 Location of neutron instrumentation in the

scientific pods 21 2.2 Detailed orientation of neutron instrumentation

in ehe scientific pods 22 2.3 Diagrammatic representation of pod orientation

angles for Shot Star Fish Prime 23 2.h Boron shield showing arrangement of the various

detecting materials 24 2.5 Arrangement of completed neutron detection

package for placement into the pods 24 2.6 Photograph of all foils ready for assembly into

a completed package 25 3.1 Neutron flux versus distance for Shot Blue Gill

Triple Prime 32 3-2 Neutron flux versus distance for Shot Star

Fish Prime 33 h.l R/V orientation for Shot Blue Gill Triple Prime. 39 k.2 R/V orientation for Shot King Fish 40

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CBVPTER i

INTRODUCTION

1.1 OBJECTIVE

The objective of this project was to measure the neutron

flux as a function of distance from high-altitude nuclear

detonations.

1.2 BACKGROUND

Neutrons that are produced in excess in both the fission

and fusion processes and pass into the media surrounding the

reacting mass have been measured during almost all nuclear-

weapon tests since Operation Sandstone. Measurements made of

the neutrons that completely escape the physical boundaries of

the device being detonated are referred to as external-neutron

flux measurements. The determination of the number and energy

of neutrons in the external environment of nuclear devices

detonated at high altitudes is of prime importance in the evalu-

ation of their effect on electronic and nuclear systems.

Both colllmated and. uncollimated flux measurements have been

made (References 1 through 23), the latter being more common. This

type of measurement has usually Involved placing detecting media at

various distances from the point of detonation. A myriad of physical

arrangements has been used to obtain measurements on the surface

and at low altitudes. High-altitude measurements have been made

by carrying the detecting media into position in pods attached

to the shot vehicle and in the pay loads of auxiliary rockets.

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In the measurements of the uncolllmted flux, the total flux at

the detecting station has been measured with no consideration

given to the angular distribution.

Neutron detectors of various types have been used. The

usual method of detecting neutrons from nuclear detonations,

however, has been by the use of small amounts of materials that

are activated through nuclear transformations Involving neutron

capture or fission. The emissions from radioactive Isotopes

produced in these materials are measured and correlated directly

with the neutron flux to which the materials hav? been exposed.

Prior to Operation Teapot, most measurements were made of

slow neutrons (using gold as a detector) and fast neutrons (using

sulfur as a detector). However, other materials, such as arsenic,

tantalum, copper, and iodine, have also been used. During

Operation Teapot, the fission-foil method of measuring fast

neutrons was first successfully used on a large scale. This

method gave the first indication of spectrum that was complete

enough to allow the calculation of neutron dose. The measurement

of neutron flux from nuclear devices detonated at high altitudes

was first attempted at Operation Hardtack. Time-of-flight

measurements were made by the Naval Research Laboratory (NEL)

(Reference 2k),a.nd threshold detectors were flown by Sandia

Corporation and Nuclear Defense Laboratory (NDL). These

measurements, although limited in scope, gave a valuable in-

sight into the external neutron environment of devices detonated

at high altitudes.

1.3 THEORY

To theoretically determine the number and energy dis-

tribution of the neutrons produced by a nuclear detonation, the

10

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following must be known: (l) the source strength, (2) the

attenuation and degradation caused by the case and the reentry-

vehicle (R/V), and (3) the manner in which the neutrons behave

as they move from the point of detonation to the point of interest.

The weapons laboratories usually have a prediction of the source

strength for standard devices; however, the complexity of the

various modifications to accommodate these devices to various

reentry vehicles make the calculation of the neutron flux and

spectrum at the exterior of the R/V difficult.

Many laboratories and scientists are now studying the trans-

port of neutrons through the atmosphere. Computer codes have

been written which follow a neutron on its flight path, and with

these codes, the calculation of the flux and spectrum at any

point is possible. However, most codes make simplifying

assumptions which, in many instances, cause the results of the

computations to be in error. A new, all-inclusive code is now

being written by Los Alamos Scientific Laboratory (LASL) in

cooperation with the Defense Atomic Support Agency (DASA). It

is expectad that this code will include not only cases at the

ground-air interface but also cases at altitudes comparable with

those that are described in this report.

11

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'V

CHAPTER 2

PRDCEDURE

2.1 OPERATIONS

During Fish Bowl, Project 2.1 participated in all

events for which the Thor was used as a launch vehicle. The

events designated as Tiger Fish, Blue Gill, Blue Gill Prime,

Star Fish, and Blue Gill Doutle Prime produced no nuclear

environment. Hbwevei, inmost instances, project instrumentation

was recovered and reused. The events Blue Gill Triple Prime,

King Fish, and Star Fish Prime, were detonated as expected,and

the results of measurements made during these events are

described in this report. Table 2.1 lists parameters pertinent

to these nuclear events.

All project instrumentation was contained in the rear

bulkhead of three recoverable scientific instrument pods. These

pods were attached to the launch vehicle and released at the

proper time during the early part of the trajectory^to place

them at various distances from the point of detonation. A

complete description of the pods can be found in Reference 26.

Figures 2.1 and 2.2 show the location and orientation of the

Project 2.1 instrumentation in the pods. Table 2.2 lists in-

fonnation pertinent to the pods for the three nuclear events.

All pods from Blue Gill Triple Prime were recovered and

returned to Johnston Island by H+8 hours. The neutron detection

packages were removed and returned to the NDL mobile laboratory

for analysis. The rear bulkhead of Pod B-2 was severely

12

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damaged; hciwever, all neutron instrumentation except that

located in Quadrant k was intact. The package in Quadrant k

was so badly damaged that no information could be obtained.

Pods 1 and 2 from Shot King Fish were returned to Johnston

Island at approximately H-H5 hours. The neut/on instrumentation

from Pod K-l was removed and returned to the NDL mobile laboratory.

The rear bulkhead of Pod K-2, which contained the neutron instru-

mentation, was missing when the pod was delivered to Johnston

Island. Only the nose of Pod K-3 was found.

The pods from Shot Star Fish Prime were returned to Johnston

Island between H+8 and H+10 hour's. Pod S-l showed aigns of re-

entry damage, and the rear bulkhead was bent near Quadrant 1.

The neutron instrumentation in that position was missing. Al-

though Pods S-2 and S-3 showed some signs of damage, all neutron

instrumentation was intact. As soon as initial examination and

preliminary photography were completed, the neutron packages

were removed and returned to the NEL mobile laboratory.

The location of the neutron instrumentation in the rear

bulkhead of the pod presumed an orientation of the pod at

detonation which would allow the instruments to look at the

burst only through their covers and protective coatings

(3/l6-inch refras 11 for Shots Blue Gill Triple Prime, and

King Fish, and 3/16-inch carbon for Star Fish Prime). Any

other orientation would place segments of the pod mass and

other instrumentation in the angle of view and consequently

Introduce unknown quantities of shielding and scattering.

The'Introduction of these unknown quantities would make in-

terpretation of both the flux and spectral data extremely

difficult.

13

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The orientation of the pods during Shots Blue Gill Triple

PrlJ» and King Pish was apparently as planned. The good

agreensnt of the neutron data from the four quadrants as well

as the general observation of hum shadows, etc., seemed to

substantiate proper orientation. During Shot Star Fish Prime,

pod orientation was estimated by Project 8B (Reference 27) by

the measurement of the X-ray shadows cast by various pod fittings.

Two angles were determined to give pod orientation. The first, 9,

was the angle between the longitudinal axis of the pod and the

burst in the plane formed by this line and point. The second

angle, *, measured the roll attitude as the angle between the

burst point and the YY-axis of the pod in the plane of the rear

bulkhead. Figure 2.3 Is a diagrammatic representation of these

angles. The angles 6 and i for Star Fish Prime are listed in

Table 2.3-

2.2 INSTRUMENTATION

Instrumentation consisted exclusively of the NDL threshold

detector system (References 13, 19, and 25). This system Is

compcsed of a series of materials activated through neutron

capture or fission by neutrons with energies above a threshold

energy. Table 2.U lists the materials used, the reactions,

their threshold energies (Et), and their effective cross-sections

(CT»ff )• ^ should be no+ed that \fi3s and Pu339 do not possess

natural thresholds. However, by the use of an enriched B10

shield, an artificial effective cross section can be produced.

The threshold energies and effective cross sections are detemlred

by the thickness and density of the boron shield. Shields with

a penetration density of 2.2 gm/drf1 of shield surface were used

during this experiment. Figure 2.^ shows this boron shield and

14

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the arrangement of the various foils within It. Although It is

not necessary to place any of the foils except the if38 and the

Pu339 in the boron shield, all foils except zirconium and gold

are assembled within it for convenience. The boron shield, the

zirconium foils in their shield, and the gold foils were

assembled in an aluminum container for placement In the pods.

Figure 2.5 shows the arrangement of these detectors. Figure 2.6

shows the foils ready for assembly into a ccmpleted package.

After exposure, recovery, and return of the foils to the

NDL mobile laboratory, the induced radioactivity produced in

the foils by neutron interactions was measured. Using

previously determined calibration constants, the neutron

flux required to cause the observed activation was calculated.

2.3 CALIBRATION

Periodic calibrations of the threshold detector system

have been made since 1956. A major recallbration of the system

was made during the period 1 April ' 1 1959« The

results of these calibrations as wi ete calibration

procedures are described in RefereriL 25«

Because of improved techniques for determining calibration

fluxes and flux depression factors, a complete recallbration of

the threshold detector system was accomplished during January

1963. Changes in the calibration constants of between 15 and

20 percent were noted for some of the detecting materials.

Others did not change at all or the change was insignificant.

Complete results of this calibration experiment are described

in Reference 28.

Because of the special equipment required for measuring

the activation induced in zirconium (see Section 2.h), the

15

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calibration of these foils was accomplished during the period

the project was in the field. The results of this calibration

are also reported in Reference 28.

The data presented in this report was calculated utilizing

the latest calibration constants. These are suimarized in

Table 2.5.

2.k COUNTING EQIOTMEOT

Scintillation-counting techniques were used to measure the

activities Induced in the various detector materials. These

techniques were selected so that the same equipment, with minor

changes, could he used for all measurements. The counters were

assembled 'rom standard, commercially available equipment.

Two types of scintillators were used. -Gamma activities

were measured with a 1- by 1 l/2-inch Nal(TL) crystal mounted

on an RCA 6655 photomultipller. In the case of beta activities,

a scintillator-type plastic phosphor replaced the N*I crystal.

The gold samples were placed on a I/16-Inch-thick aluminum

holder for measurement. This holder was machined to fit on

the Nal crystal. The electronics system was biased at approxi-

mately 300 kev which permitted measurement of the Ull-kev gamma

rays emitted byAu198. The calibration and monitoring of the

electronics system was accomplished with an Sb136 source.

The equipment used to measure the gamma activity resulting

from the mixed fission products in the fission detectors (l^3e,

Pu339, Np3*7, and l^38) was exactly the same as that used for

measuring the activity of the gold folia. In this case the

bias of the system was set at 1.1 Mev. The l^36, Pu339, and

l^3a samples were counted on a l/8-inch-thlck brass absorber

while the ''Irr;337 samples were counted on a 3/16-inch lead

16

■ * •-

^...ij'lt.j..:.^-*..*...^^.*.*:..^-?.■<■*■:. ■.:. t..-.\i\:C. ■....A..^.^-.^.; >.-^-i\<^-^^■■.^..■i.■-^^/,.-.■-:■^.^A^lJ^^J^yy^|^|1^|^^||^^L

^^^^^^^^^Wff^^^W^rfl^fffl^y^T1?^-' WfWWWW 'l*L" ^* V ^'J.' ^' ',!* '■'' v* 7.m *:' '■.,'1.m TT^'TTT '■

absorber. This system was calibrated and monitored with a

Co60 source.

The Na34 produced In the Al and Mg detectors was measured

on the same system as the fission detectors,using the 1.1-Mev

bias and the l/8-lnch brass absorber.

In measuring the beta particles emitted by the P33

produced by the S33(n,p)P33 reaction, the plastic scintlllator

previously described replaced the Nal crystal in the counting

system. The sulfur samples were placed directly upon the

scintlllator. The bias of the system was set Just high enough

to exclude noise. A natural uranium source was used to monitor

this system.

Zlrconlum-89, formed by the Zr^0 (n,2n) Zr89 reaction, is

a positron emitter. Since the foils used were natural

zirconium (51.5 percent Zi^0), other reactions producing other

beta and gamna emitters are possible. For this reason much

care must be taken to measure only the positron from the Zr" .

Since the direct measurement of the positron would require some

kind of a magnetic spectrometer, it Is much simpler to measure

the positron-annihilation radiation. When a positron and

electron annihilate, two quanta of gamma energy are produced.

The fact that they must be emitted l80 degrees apart in order

to conserve momentum makes this measurement not only possible,

but also easily acccniplished. Two 3-inch Nal(Tl) crystals

with their photomultlpllers were assembled with the crystals

facing each other. The Irradiated zirconium foils were then

placed in an aluminum holder between the crystals. The

electronics used with this system required not only a coincidence

between the two crystals hut that the coincidence occur with

17

■>■- .'. '.W LV K J ITJ. <f\.. iCn STV n ,_■ »Ji tJLiJi.

.■< v r«* V "." V "•■' ' ."■■ -■-

nrrwv^T^^^T'^r^-'*'. -n,m,Hi,'u|ij*i"|i »«'I'mi'ii "j" ■'.'.■''^ i'j .'.'i^."^1.' wr? -1 ji«"1.1 n■.■"■i jyj v.'uv»-'« "n j» M^1. 'TCr1'.

'A

an energy between UOO and 600 kev. Sodlim?3, which Is also a

positron emitter, was used to monitor this system.

TABLE 2.1 PERTINENT PARAMETERS FOR SHOTS BLUE GILL TRIPLE PRIME, KING FISH, AND STAR FISH PRIME ________

..A

TABLE 2.2 POD INFORMATION PEE SHOTS BLUE GILL TRIPLE PRIME, KING FISH, AND STAR FISH PRIME

Event Pod Distance from Point of

Detonation

Blue Gill Triple Prime

B-l B-2 B-3

King Fish K-l K-2 K-3

Star'Fish Prim

S-l S-2 S-3

Planned Actual km

2500 ft 1+000 ft 6000 ft

1.0 l.k 2.1

1.9 km 2.4 km 3-3 km

2.5 3.8 2-9

7.5 km 10.0 km 1^.0 km

8.7 12.2 23.4

18

-^ -'■'—.. - -' ■ -• -' '■ -■• - "-• - --_,--. "-"' -" ■

rj-r-^^v1 ^-n --..-'-.. ~, rr^i i -v. -^ i -. ■ -.'%' -vi -M ■-.',-.'-.■ -v i

T/VBLE 2.3 POD ORIENTATION AJMGLES FOR SHOT STAR FISH PRIME

POD 9 9

S-l

S-2

S-3

135

^3

1*1

61

0

35

TABLE 2.1* DETECTING MATERIALS, REACTIONS, THRESHOLD ENERGIES, AND EFFECTIVE CROSS SECTIONS

Detecting Material Reaction

Threshold Energy

Effective Cross Section

bams

Gold Aul97(n,Y)Au19a a 1/v

If36 Fission 1.5 kev t 1.7

Pu339 Fission 10.0 kev b 1-7

Np337 Fission 0.63 Mev 1.6

tf36 Fission 1.5 Mev 0.55

Sulfur S33^,?)?33 3.0 Mev 0.30

Magnesium MT" 6.3 Mev O.lll*

Aluminum Al '9 8.1 Mev 0.183

Zirconium Z^0(n^n)Zra9 12.0 Mev 0.28

a Öt'tector for room thermal neutrons with upper cut-off at 0.3 ev h Threshold and effective cross section with boron shield (see

text).

19

'1 ."\ -

kfL>ji^^A^.JCKMIX^A:. ■.-*.<..ii\.n:^.v..i-^..w.;::.^„^v. v..-:..v..-^.. i..-.V-r.v.v.'.-r.V.<., ^^^ ■.•-■. -;. -,." j.,-..;.

■ ■■■I* 11 wmm 1 --c-v"-' v '^rj \rj .,. .j ... ,... ,.. , r^-;.>- ■.■ ■ ■ - '. ' "■»""n^ r f*1«1 f" T—V

TABLE 2.5 CALIBRATION NUMBERS

Detector Conditions Calibration No.

Counts/min/gm

Gold

Pu239

Np: 337

\f 38

l/2-lnch-diaineter x 2 mil-thick foil counted on a l/l6-inch Al|

absorber

15/l6-inch-diameter foil counted on l/8-lnch-thick brass absorber

15/l6-inch-diameter foil counted on a l/8-lnch-thick brass absorber

3/U-lnch-diameter foil counted on a 3/l6-inch-thick lead absorber

15/16-lnch-diameter foil counted on a l/8-lnch-thick brass absorber

Sulfur l-inch-diameter 2-grani pellet placed inside the boron shield

Magnesium 1-lnch-dlameter foil counted on a 1/8-inch-thick brass absorber

Aluminum l-inch-diameter foil counted on a l/8-inch-thick brass absorber

Zirconium l-inch-diameter foil counted on , positron annihilation equip- ment

Note: Calibration number for the fissionable materials based on activity at H+10 hours. All other numbers based on activities at 0 time.

20

« .. « ■ . . . ... > ^ ,. ■ . ^ ■" > r *■ '--* \i ^A-.AV-.V.."

-- - ■■ '' *' -' ■.-1.1-'-'.-

n^^^^^ .M.u .tf'.-yj j i | fm | IMIM.P» ' '!.' ' * "^ v- " ■ ■ v *->r

^T"V^TrT"'^','TL^^

c 0

71

c K

£ 3

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c —« a ■M -j

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21

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--'--':^ ■•"■■• I UM.

mm^immmmmm ' wm^^i^mm ^^r

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c

E

en c c p *-» 3 a c

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4-1 dt c V u o

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22

•j.".^,-->>lk".^\-. -^■ ■ ■■-' ■• ■

■ ■. .'■■.\k-,' .V ...■; .\.•:■...■.,:■.... . . . /■ . .-, . ... . ^.^^^^.^.^^„^L^^^-fr,

^^^r* -^: * '_■ 1 -\.- ^ -_■ - "^n"v" wmr^r^^V^ nil i. ii _i. i i I i i, . i i] i i. i. i i, ■ i. ■ ^ ti i \i *\. mi mi mi wy ^.. ■

OFF-AXIS ANGLE ft

POO LONGITUDINAL AXIS

RST

POO ROLL ANGLE <fr

UMIBILICAL FITTING

INSTRUMENT BULKHEAD

Figure 2.3 Diagrammatic representation ot pod orientation angles for Shot Star Fish Prime.

23

.\V;Vi':v': liMmljailL iu^*. r* ■> .v--■>",,.i.', .'. - -t - .v».-".,,A .■, '. . .'».A ^ 1 .• .,■ i ■«_•./■. \ ^Y^AH ;.,i "L ^:, .■^:. ■•^.'..•^'v.^'^^A ■^'1 .■■.;„i.-^^,.^-..--■" .^•. _'..^'1-^\-_'. .-v,.

c 0 (fl 1-. ■a

i a

c OJ ri

T3 (11

0 01 c Q. S 0 u

c 0)

r 0

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m c 01 a s h <u O so c 11

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in ä CM c

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a n ä (U

s ■o

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a 0»

e a» g ca i^ ii «

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ta jS ■o

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£ "3

24

.'•C--v-.'-'.--v...-:.,--v.; >A..^.i^J.^r-.^r..^'-^ L.*, L. - läüa

■IK -. A ^ '. ^-■.■•■, . .r.

VTA.!?..

Figure 2.6 Photograph of all foils ready for J>S.- -mbly into a completed package. (NDL photo)

25

Tx^ ^F■ZT1 x-nwjnn, KrTW

J Pwi ^. ■."■' ^ ^^. ^p^^mp^wyyoyr^^^^^^^' i * v ".' '.^ »^ »* p* r''.'' "^ T* »V r'l";' ^''.'■ '."-'^

CHAPTER 3

RESULTS

3.1 NEUTRON FLUX

The results of the tieutron flux measurements made during

Shots Blue Gill Triple Prime, King Fish,and Star Fish Prime

are presented in units of neutrons per square centimeter for

each detecting material and slant distance. For all materials

this is the total number of neutrons above the effective

threshold of that material.

Tables 3.1 and 3.2 list the data from Shots Blue Gill

Triple Prime and King Fish, respectively. Data is missing

from positions and pods for which detector packages were

lost, as explained in Chapter 2. Table 3«3 lists the data

from Shot Star Fish Prime. The apparently anomalous measure-

soents in quadrant 3 of Pod S-l are attributed to pod orientation

and are not included in the average. The wide spread in the

data from the other pods is also attributed to shielding and

scattering caused by the mlsorientation of these pods. The

data for Shots Blue Gill Triple Prime and Star Fish are

plotted in Figures 3»1 and 3-2, respectively.

Several researchers have expressed a special interest in

the gold foil information from these events. This information

is therefore prese-ted separately. The counting rates in

relative counts per minute are presented as well as the

difference [calculated as (Ng - 1.025 Nc) where NB is the

counting rate of the bare foil and N« is the counting rate

26

•. -.->■■

rwrr91?1','' »." j« ,'''■;« '.''?■ .''.i»".• ^ 'j w»'.'":Jv"'.' ■ T 'V " '.'■' i'.' ■"' ^r ■ "^,l^l^^^■^ vjv; ■--.'-

of the uadffllum-shielded foil]. The flux below 0.3 ev is

generally calculated by multiplying this difference by the

calibration number shown in Table 2.5' However, because

of the doubtfulness of the validity of these small differences,

no flux values have been calculated. These data are presented

in Tables3.U, 3.5, and 3.6 for Shots Blue Gill Triple Prime,

King Fish, and Star Fish Prime, respectively.

3.2 NEUTRON DOSE

Neutron dose is presented in Table 3«7 as first collision

rads for each pod. These results were calculated by applying

the dose per neutron per square centimeter at the average

energy between the thresholds of the various detecting materials.

The following formula gives the dose-flux relation:

Dose (rads) = Cl.O (Np^N^,) + 2.5{^-\) + S-S^-Ng)

+ ^(Ng-Nug) + 5.3(1^-%!) + 5.9(NA1-NZr] (3#1)

1.07X10"9

Where the dose is in rads and N^, N , N~, N , N« , NA1)and

N2r are the number of neutrons per square centimeter above

the thresholds of plutonium, neptunium, uranium, sulfur,

magnesium, aluminum, and zirconium, respectively. No spectral

effects were considered.

27

^3^-^33 ae.le.recf.

HJIUA l'Jl.M ^ l»y^'y ^»j^jiimM" i.*^* ,i.J.J'-'l >'.

CHAPTER k

DISCUSSION

k.l NEUTRON FLUX AND DOSE

The neutron flux data presented In Chapter 3 for Shots

Blue Gill Triple Prime and King Fish are consistent, and no

anomalies appear. The small variation in the data among the

detectors placed in the various quadrants of the same pod

indicates that the measurements were not affected by pod

orientation. It would also tend to indicate that shielding

or scattering by adjacent instrumentation was minimal; however,

it is obvious that such was not the case for Shot Star Fish

Prime. From the measurements of pod orientation shown in

Chapter 3, it can be concluded that the detector package

located in Quadrant 3 of Pod S-l was looking at the burst point

through a large part of the pod mass. The detector packages

located in Quadrants 2 and k, on the other hand, looked at the

device through the outer flange of the pod. However, it is

expected that scattering and degradation In the pod mass in-

fluenced the measurements to some extent. This is substantiated

by an examination of the flux ratios which show a quite different

spectrum in the vicinity of Pod S-l than in the vicinity of Pods

S-2 and S-3. The rather wide spread in the measurements made

in Pqd S-3 can also be attributed to pod mlsorientation.

Special mention should be made of the gold foil information

presented in Chapter 3- No values are presented for the neutron

flux below 0.3 ev even in instances when a difference between

34

V■"."•'.■-'/•"■ ."v. •,"%-■■".'•_,■•_-"■, v"v'.'''/%Cv>v"' ■ -'.'■',-'.'''S*. ■'■'■':-,' v'»."'•,■•."'•.■"•.''•." '.'" • V- '.'■'.'■■■'■>V"•"v"-'."" Vv'v' .'''■■''-■'.■ 1 •■.>■."-"-"-'-'1..

^>^^y^^^^*^^^^^^^w,"ww : 'j'-y"'! paiii^iMi^j mi, ,m„, IJ»V"P'J ■ r.'i »^^ TI »■•■'■ vi--v!''-T;i-vv,".,t-^" ■■ -.«-T-. -.W -...-.■... .,-■_.

the unshielded and the cadmium shielded foils exists. It was

expected that some moderation would occur In the pod mass (l;200

pounds), but the extent of this moderation was not estimated.

Considering the number of parameters which can affect the amount

of activation In gold foils, the significance of a small difference

between the counting rates of the unshielded foil and the cadmium-

shielded foil in the second decimal place is questionable; and

it is certain that a difference in the third decimal place is

not significant. Estimates of the thermal flux by other

meana (Reference 29), however, agree in order of magnitude with

the values presented here.

As mentioned in Chapter 3, the neutron doses presented are

single-collision rads. Should multiple-collision doses be desired,

they may be calculated from the following formula:

D = [0.3^ N^ + l.OSCNp^NNp) + 3.98(1^-10 + h.52 (Nu-Ng)

+ 5.65(Ns-NNfe) + 7.35(1^-%) + 7-55 (NA1-NZr) (U.l)

+6.90 NZr] 1.07X10"9

Where:

NAu' ^W %' NIP Ns' NAP NMg' NZr' are the nvmteT of

neutron above the threshold of gold, plutonium, neptunium,

uranium, sulfur, aluminum, magnesium and zirconium, respectively.

1+.2 IATA RELIABILITY

The threshold detector system is assumed to have an internal

accuracy of i5 percent and an absolute accuracy of ±20 percent.

The foils exposed during all events exhibited activities high

enough to permit good statistical accuracy in counting. The

decay of all foils were checked against standard values, and all

were correct. Except in cases where pod orientation interfered

35

■.■.■•.\^..-v

^^^yrv'ivivwjirj"..""'".' '*'•*•'' >,■"■'.!•,"'Tr:'v.,y:,w'."r:»,,.i^,-"u^'^ T^ngm^T^rreT^T^TT

with the measurenents, there la .:o reason to believe that the

measurements made during this operation are not as reliable

as any ever made with the threshold detector system.

U.3 COMPARISON WITH PREDICTIONS

When comparing the data presented- In this report with other

data or predictions, three things must be kept In mind: (l) The

inherent accuracy of the threshold detector system, (2) the

inaccuracies caused by pod misorientatlon during Star Fish

Prime, and (3) the difference in R/V configurations and

orientation between Blue Gill Triple Prime and King Fish. The

first two items have already been discussed. The relative

importartce of the third has not been quantitatively estimated;

however, that it will affect the measurements is unquestionable.

The R/V for Blue Crill Triple Prime was oriented with tha

These

orientations and configurations are shown in Figures k.l and

k.2 for Blue Gill Triple Prime and King Fish, respectively.

Calculations of the expected fluxes above the thresholds

of the various detectors were made by personnel at Kaman

Nuclear, Colorado Springs, ".Colorado. Table k.l lists predicted

and measured values of the flux above 10 kev (Pu339), 3 Mev

(sulfur), and 12 Mev (zirconium). An examination of this _table

will show that the total measured flux (above 10 kev) was

36

■'•■ .-- ."■.-- ."-V I^H^i .-.V. sJ.S^-:^.-j ,-■ ■,•.:■,--•,'■*■■ „■■V. C. ,■■ .. ,,'. V-^..^., v. ■,'. [ ■ | ■ - .:wv-:r».n'..-,;w./1,a.v4 3',i.v\. ^^^^j^^^^^jjj^^!^^^

A good Indication as to change in spectrum between pod

positions or shots may be had by comparing the ratio of the

flux as measured by the various detectors to that as measured

by plutonium (total flux). These ratios are presented in Table

U.2. It can be seen from this table that there is a slight change

in spectrum as distance increases for Blue Gill Triple Prime

and that this spectrum is different from that for King Fish

^ The values for Star Pish Prime are rather

non-conclusive because the effect of the mlsorientation of

the pods during this event is questionable.

37

v.-vv v-. »v ■■>"■..•> . „> .-.■

',v.% ,> ,•-!."- .>',••■ ■>."- ,'•>"- -'■■ -"■ - - ••■- - - ■• - ^■T-vVv^ --•,■ ".■"," v >".,- '.b".- ,■ '■• '■■• '■ '-■ '■:'■• -■ ■". ■. -'. •". -•. ■ »^-'» *

mwm, mMww I I ■_■ WJ|I»I||I1I I IIJ'JIMtPJ1* i M ^J ^1 "JT » .^ P « VV« "l1 V-1 V« ' l1'^1 « U «.V "> ' l11»^ ^

r.-

CHAPTER 5

CONCLUSIONS AND RECOMMENDATIONS

5.1 CONCLUSIONS

Measurements of the neutron flux were igade at three

distances from Shot Blue Gill Triple Prime.

Only the neutron detectors from the 2.5"km pod^were

recovered after King Fish. These detectors showedJ

Measurements made during Shot Star Fish PriM showed

-JShat neutrons with energies greater than 1.5 kev varied from

The measured total flux (above 10 kev)1.

; ■ The project obtained data in all events in which it

participated and can be considered a success.

5.2 REC0MMENIÄTI0NS

None.

41

-- .>i.v,--V

Ii;^ll^K"T)i'Tjn»TM~H-lw'iM. "1 4-"■ V ^ ^_T V ^^p^yiPT1^Wy,U.'lJ»l.l_'^1« V»B7r'!l_Wl>»B^^,»B''^T"r"r'V.« »." fn;' «■ »•■ v-r' r^i^.n»-.»-^' •'■'.'.T

REFERENCES

1. C. W. Luke and others; "Neutron-Flux Measurements";

Project 2-51, Operation Redwing, wr-1313, 1959; Chemical

Warfare Laboratories, Army Chemical Center, Maryland; SECRET-

RESTRICTED DATA.

2. Scientific Director's Report, Operation Sandstone,

Volume 18, Annex R, Part K and Addendum, 19^8; SECRET-

RESTRICTED DATA.

3. W. Ogle and others; Operation Ranger, Los Alamos

Scientific Laboratory Report LAB-J-2095; "Neutron Measurements";

SECRET-RESTRICTED DATA.

k. J. Allred and others; "Neutron Measurements"; Pre-

liminary Report of Group LAJ-3, Greenhouse, 1951; SECRET-

RESTRICTED DATA.

5. T. D. Hanscome and others; "Neutron Flux Measurements";

Project 2.3, Operation Tumbler-Snapper, WT-52'l-, 1953; Office of

Naval Research, Washington, D. C; SECRET-RESTRICTED DATA.

6. D. K. Willet, T. D. Hanscome, and L. W. Flagg;

"Neutron Flux Measurements"; Project 2.3, Operation Upshot-

Knothole, WT-720, 1953; Office of the Naval Research, Washington,

D. C; SECRET-RESTRICTED DATA.

7. T. D. Hanscome, D. K. Willet, and A. Brodsky; "Neutron

Flux Measurements"; Project 2.3, Operation Castle, VT-91k,

October 1955; Naval Research Laboratory, Washington, D. C;

SECRET-RESTRICTED DATA.

8. P. S. ffeirris and others; "Physical Measurement of Neutron

42

'vv-%V-l-"-y-j-"-i"-'-'-y^\

and Gamma Radiation Dose from High Neutron Yield Weapons and

Correlation of Dose with Biological Effect"; Pro-ject 39. 7,

Operation Teapot, WT-1167, 1956; Los Alamos Scientific

Laboratory, Los Alamos, New Mexico; SECREI'-RESTRICTED n\TA.

9· W. A. Biggers and others; "External Neutron and G6mma

Flux Measurements by Sample Activation"; Annex. 1. 5, Part II,

Section I, Operation Greenhouse, WT-114, 1957; Los Alamos Scientific

I.&boratury, Los Alamos, New Mexico; SECRET-RESTRICTED IY>.TA.

10. W. A. Biggers and others; "External Neutron Measure­

ments with Threshold Detectors"; Project 17.1, Operation Upshot­

Knothole, WT-826, March 1955; Los Alamos Scientific Laboratory,

Los Alamos, New Mexico; SECRET-RESTRICTED D\TA.

11. W. A. Biggers and others; "External Neutron Measurements";

Project 14.1, Operation Cast le, WT-952, October 1955; Los Alamos

Scientific laboratory, Los Alamos, New Mexico; SECRET-RESTRICTED

IY>.TA.

12. D. L. Rigotti and others; "Neutron Flux From Selected

Nuclear Devices"; Project 2.3, Operation Plumbbob, WT-1412, April 1960;

Chemical Warfare Laboratories, U. S. Army Chemical Center,

Maryland; SECRET-RESTRICTED IY>.TA.

13. J. w. Kinch and others; "Neutron Flux From Large-

Yield Bursts"; Project 2 . .-, Operation Hardtack, WT-1622, May 1960;

Chemical Warfare Laboratories, Army Chemical Center, Maryland; SECRET­

RESTRICTED DA.TA.

14. D. L. Rlgottl aad others; "Neutron Flux From Very-Low-Yield

Burst"; Projects 2AA/2.11/2.12a, Operation Hardtack, WT - 1679,

1960; Chemical Warfare LabonLtories, U. s. Army Chemical Center,

Maryland; SECRET-RESTRICTED IY>.TA.

15. G. s. Hurst and others; "Techniques of Measuril]8

Neutron Spectrum with Threahold Detectors-Tissue boee Determination";

The Review of Scientific Instrument, Volume 27 1 No. 3 1 March

1956: UNCLASSIFIED.

16. G. s. Hurst, R. H. Richie, and H. M. Wilson; Scientific

Instrument 22, ·981, 1951; UNClASSIFIED.

17. K. M. Case 1 F. De hoffman, and C. Placzek; "Introduction

to the Theory of Neutron Diffusion"; Volume 1, June 1953; Loa

Alamos Scientific Labon.tory, Los Alamos, New Mexico; UNCLASSIFIED.

18. Samuel s. Holland and Paul I. Richards; "Penetn.tion of

Neutrons in Air"; AFSWC-TR-55-27, September 1956; Air Force Special

Weapons Center, Ki:tland AFB, New Mexico; SECRET-RESTRICTED ~~.

19. J. H. McNeilly and J. W. Kinch; "Recent Developme ta

in the Threshold Detector System as Used by the U. • Arrrr:t

Nuclear Defense Laboratory"; NDL-TR-15, October 1961; u. S. Arrrr:t

Nuclear Defense La'ooratory, Arrrr:t Chemical Center, Maryland;

UNCLASSIFIED.

20. Health Physics Annual Re-port for Period Ending July 31 1

1959, ORNL-28o6, P. 173-174; Oak Ridge National Labon.tory, Oak

Ridge 1 Tennessee; October 1959; UNCLASSIFIED.

21. D. J. Hughes and J. A. · Harvey; "Neutron Cross Sections";

BNL Report 325; 2nd Ed., January 1960; Brookhaven National

La bon. tory 1 Upton, New York; UNCLASSIFIED.

22. c. J. Cosenza; "Vuinen.bility of Missile Structures

to Nuclear Detonations"; Project 8.6, Open.tion Hardtack, WT-16521

1962; Wright Air Development Division, Wright Patterson Air Force

Base, Ohio; SECRET-RESTRICTED ~.

23 .; · T. D. Fans come and others; "Neutron Flux From Very­

High Altitude Bursts"; Project 2.6, Operation Hardtack, WT-1623;

May 1961; U. S. Naval Research Labon.tory, Washington, D. C.;

SEC:Jmr-RESTP.ICTED n\~.

^^^^^^^^■^^t MM Hi Hill. I [, I IILI 11,111 I I M I'MJ. .L.MBl^ M.. Jl.^.

2k. P. A. CaldweU and others; "Nuclear Radiation From a

Detonation at Very-High Altitude (c)"; Project 2.7, Operation

Hardtack, ITR-1621+, July 1958; U. S. Naval Research Laboratory,

Washington, D. C; SECRET-RESTRICTED DATA.

25. J. W. Kinch and John H. McNellly; "An Activation Type

Neutron Detection System and its Calibration"; CWLE-2282; 1959;

Chemical Warfare Laboratories, Army Chemical Center, Maryland.

26. Arthur J. Starnes et al; "Pod and Recovery Unit

Fabrication"; Fish Bowl Project 9.4b, Operation Dominic,

POR-2041; Air Force Special Weapons Center, Kirtland AFB,

New Mexico; SECRET-RESTRICTED DATA.

27. C. M. Gillespie et al; "Nuclear Weapon X-ray Effects

as Measured by Passive Instruments"; Fish Bowl Project SB,

Operation Dominic, POR-2038; Air Force Special Weapons

Center, Kirtland AFB, New Mexico; SECRET-RESTEICTED DATA.

28. McNellly, John H.; "Calibration of Threshold

Detectors During January 1963"; U. S. Army Nuclear Defense

Laboratory, Edgewood Arsenal, Maryland (to be published).

29. Kinch, J. W., Jenkins, R. W.; "Gamma Radiation

Measurements"; Project 2.2, Fish Bowl Series, Operation Dominic,

POR —2013; U.S. Army Nuclear Defense Laboratory, Edgewood

Arsenal, Maryland.

45-46

/Vi^ V 7 c^ *- &"

N»,^.,- vy.- ■.■■->■.- v ■■.v-v\y.--.--v-v-V--^ .r ^ A m...- h.A »■: